Multi channel memory with flexible code-length ecc

ABSTRACT

Apparatuses and methods for error correction and detection of data from memory on a plurality of channels are described. An example apparatus includes: a first memory cell array including first input/output nodes; a second memory cell array including second input/output nodes and third input/output nodes; a first error correcting code (ECC) control circuit including fourth input/output nodes and fifth input/output nodes; and a second ECC control circuit including sixth input/output nodes coupled respectively to the third input/output nodes of the second memory cell array. The fourth input/output nodes of the first ECC control circuit are coupled respectively to the first input/output nodes of the first memory cell array. The fifth input/output nodes of the first ECC are coupled respectively to the second input/output nodes of the second memory cell array.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 14/852,232 filed on Sep. 11, 2015, which is incorporated herein by reference, in its entirety, for any purpose.

BACKGROUND

In a semiconductor memory device, memory cells may be susceptible to single-bit errors based on a transient error or a soft error. The single-bit error may be due to a transient error caused by noises from surrounding components in the device with high-density. A soft error may be caused by background radiation. Memories have been developed that include error detection and/or error correcting codes (ECC) to correct these single-bit errors. The error detection and ECC are typically a simple parity check error detection or a relatively simple single-error-correcting (SEC) Hamming code, a single-error-correcting-double-error-detecting (SEC-DED) extended-Hamming code, etc. For high-precision systems that require high reliability, such as network applications, any critical error which causes the system to operate incorrectly is not acceptable and these simple ECC codes may not be sufficient. Thus, these high-precision systems tend to utilize more complex codes which are capable of correcting multiple bits, such as a double-error-correcting-triple-error-detecting (DEC-TED) Bose-Chaudhuri-Hocquenghem (BCH) code and a Reed-Solomon code. However, the complexity of these codes having more check bits may result in increased die size and longer processing time, neither of which may be desirable in high-speed and compact memory applications.

In recent years, there has been an effort to correct memory bit errors while maintaining higher data transfer rates and reducing die sizes. For example, U.S. patent application publication 2014/0189468 A1 describes memory devices including control circuitry which is able to adjust a size of one or more of the ECC coverage areas. Another example is U.S. patent application publication 2015/0074493 A1, which describes a semiconductor device including a reduced number of reference cells for error detection and correction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a semiconductor device in accordance with the present disclosure.

FIGS. 2(a) and 2(b) are block diagrams of error correction blocks according to the present disclosure.

FIGS. 3(a) and 3(b) are simplified block diagrams of data bits, check bits and check matrices of a semiconductor device according to the present disclosure.

FIG. 4 is a schematic diagram of multi-channel error correction processes and data flows according to the present disclosure.

FIG. 5 is a block diagram of multi-channel error correction processes and data flows among components according to the present disclosure.

FIG. 6 is a schematic diagram of multi-channel error correction processes and data flows according to the present disclosure.

FIGS. 7(a) and 7(b) are block diagrams of multi-channel error correction and data flows with optional switches between two different multi-channel modes on two channels according to the present disclosure.

FIG. 8(a) is a sample parity check matrix transferred across two channels according to the present disclosure.

FIG. 8(b) is a block diagram of logic circuitry for the multi-channel error correction and data flows of FIG. 8(a).

FIG. 9 is a block diagram of logic circuitry for a syndrome decoder according to the present disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

High data reliability, high speed of memory access, and reduced chip size are features that are demanded from semiconductor memory. Multi-channel memories have been developed to provide memory systems with faster memory access and improved data throughput at lower latency. To maintain high data reliability, ECC has been included in these multi-channel memories. For example, for applications where memory systems are handling data for continuous or possibly non-stop operations, multi-bit data correction codes such as a BCH code with a DEC-TED level of detection/correction ability have been employed. For example, for data having 128 bit data length using the BCD code, 17 check bits (which may also be referred to as a “parity bits”) are used resulting in a total of 145 bits of data and ECC bits. In order for BCD data correction to work sufficiently, a number of bit errors tolerated should be less than three among a total of 145 bits. While additional check bits could be included to provide increased error correction capability, this approach typically results in a larger die size and longer processing time.

A memory including memory cell arrays may include a plurality of channels instead of a single channel having a large code length, which may provide relatively high bandwidth and fast data access. An example configuration may have each channel receiving and providing a same number of bits from an array or arrays. ECC processing may be divided among the channels. For example, a memory may include two channels, where each channel is used for about half the code length. Separate ECC processing may be used in each channel to provide half error rate and processing time. In an example having 145 bits on two channels, it is possible to divide the 145 bits into one channel with 73 bits and another channel with 72 bits. Each channel may have a bit-width of 80-bits. Given the 80-bit width of each channel, 7 bits are available for check bits for the second channel whereas 8 bits are available for check bits for the first channel.

TABLE 1 Data Bits Check bits Check bits Check bits (SEC/SEC-DED) SEC SEC-DED DEC-TED 16 5 6 11 (12-26) 32 6 7 13 (27-57) 64 7 8 15  (58-120) 128  8 9 17 (121-247)

Table 1 shows several relationships between the number of data bits to be checked for potential errors and the number of corresponding check bits for different levels of error correction and detection such as SEC, SEC-DED and DEC-TED. Hereafter, a notation (c, d) is used for describing a code with a code length c and a data length d. For example, it is possible to execute SEC-DED ECC for up to 120 bits with eight check bits. However, only 57 bits can be properly checked and corrected applying SEC-DED with seven check bits. As applied to the example of the first and second channels previously described, this implies that while the eight check bits for the first channel are sufficient to provide SEC-DED ECC for the 72 bits of data, the seven check bits for the second channel are not sufficient for SEC-DED ECC for the 73 bits of data.

As will be described in more detail below, semiconductor memories according to the present disclosure include error detection and correction where some data bits on a first channel are assigned to an ECC control circuit on a second channel using a set of check hits of the second channel. By assigning some data bits on the first channel for error detection and correction on the second channel, it may be possible to provide ECC for a larger total data size compared with using check bits available on the respective channels.

Various embodiments of the present invention will be explained below in detail with reference to the accompanying drawings. The following detailed description refers to the accompanying drawings that show, by way of illustration, specific aspects and embodiments in which the present invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present invention. Other embodiments may be utilized, and structure, logical and electrical changes may be made without departing from the scope of the present invention. The various embodiments disclosed herein are not necessary mutually exclusive, as some disclosed embodiments can be combined with one or more other disclosed embodiments to form new embodiments.

FIG. 1 is a block diagram of a semiconductor device in accordance with the present disclosure. The semiconductor device 10 includes a memory core 11 that can store data. The memory core 11 has a memory cell array 11′ that can store user data (DQ) and parity data used as error detection and correction information for ECC. The memory cell array 11′ has multiple word lines WL, multiple bit lines BL, and multiple DRAM cells arranged at intersections of the word lines WL and the bit lines

The semiconductor device 10 includes an input receiver circuit 13 that receives an external command address signal CA and generates an internal command address signal ICA based on the external command address signal CA. In order to access the memory core 11, the semiconductor device 10 includes an access control circuit 12 that controls operations of various circuit blocks in the semiconductor device 10 based on the internal command address signal ICA. The access control circuit 12 has a row decoder XDEC, a column decoder YDEC, and a refresh control circuit 20. The row decoder XDEC accesses to the memory core 11 in a row direction, while the column decoder YDEC accesses to the memory core 11 in a column direction. The refresh control circuit 20 receives a refresh signal IREF, which is one type of the internal command address signal ICA, the row address is supplied and a refresh operation is executed. Additionally, the refresh control circuit 20 may also receive an error signal ERR from an error correction block 15 to execute the refresh operation.

When a column access is performed to the memory core 11, the memory cell array 11′ is coupled to a main amplifier 14 via a main data line MIO. The main amplifier 14 has a read amplifier RAMP and a write amplifier WAMP. The read amplifier RAMP can be activated at execution of a read operation, to amplify the user data DQ and the parity data read out from the memory cell array 11′ via the main data line MIO. The write amplifier WAMP can be activated at execution of a write operation, to write user data DQ and error correction information ECC to the memory cell array 11′ via the main data line MIO.

The main amplifier 14 is coupled to a data input/output circuit 16 via the error correction block 15, which will be described in detail later. At execution of the read operation, the data input/output circuit 16 transmits the user data DQ corrected by the error correction block 15 as output data of the semiconductor device 10. At execution of the write operation, the data input/output circuit 16 receives input user data DQ to the error correction block 15 from external terminals.

The semiconductor device 10 includes a clock receiver circuit 17 that may receive complementary external clock signals CK and CKB and that may generate an internal clock signal PCLK. The internal clock signal PCLK is supplied to a timing generator 18 and to a DLL circuit 19. The timing generator 18 can generate an internal clock signal ICLK, based on the internal clock signal PCLK. The internal clock signal ICLK may be supplied to various circuit blocks including the access control circuit 12 and the amplifier 14. The DLL circuit 19 can generate a phase-controlled output clock signal LCLK, based on the internal clock signal PCLK. The output clock signal LCLK may be supplied to the data input/output circuit 16, where the output clock signal LCLK determines timing of outputting user data. DQ from the data input/output circuit 16 to the outside.

FIGS. 2(a) and 2(b) are block diagrams of error correction blocks according to the present disclosure. FIG. 2(a) illustrates two channels provided for coupling between a memory core and the error correction block 15. In order to achieve a high bandwidth, a total 145 bits including 128 data bits and 17 check bits from the memory core may be divided into two channels as a first channel (Ch-P) with 73 bits and a second channel (Ch-Q) of 72 bits. In FIG. 2(a), a memory core 200 includes a first 80-bit memory cell array 201 a and a second 80-bit memory cell array 201 b provided for Ch-Q and Ch-P respectively. On Ch-Q, a first node 202 a of the first memory cell array 201 a is coupled to a fourth node 203 a of a first ECC control circuit 204 a for executing SEC-DED process. Similarly, on Ch-P, a second node 202 a of the second memory cell array 201 a is coupled to a third node 203 b of a second ECC control circuit 204 b for executing SEC process concurrently with Ch-Q. Therefore, the embodiment in FIG. 2(a) allows Ch-P and Ch-Q to have extra 7 bits and 8 bits respectively, which may be available for ECC processing on both channels. As previously discussed with reference to Table 1, it is possible to execute SEC-DED ECC for up to 120 bits with eight check bits. However, only 57 bits can be properly checked and corrected applying SEC-DED with seven check bits. Thus, for Ch-Q, SEC-DED processing can be executed because 8 bits are available for this ECC process of 72 bits (less than a maximum of 120 bits that can be corrected using SEC-DED). However, SEC-DED processing cannot be executed for Ch-P because only 7 bits are available for the ECC process of 73 bits (greater than the maximum 57 bits that can be corrected using SEC-DED) which are sufficient for executing SEC but insufficient for SEC-DED processing.

While 8 bits in Ch-Q (80, 72) are sufficient to execute SEC-DED processing up to 120 bits while 7 bits in Ch-P (80, 73) are sufficient to execute SEC-DED processing up to 57 bits, as shown in Table 1, it is possible to apply SEC-DED on a total of 145 data bits in Ch-P and Ch-Q by keeping the number of bits on Ch-P under 57 bits while increasing the number of bits on Ch-Q up to 120 bits.

In FIG. 2(b), similarly to FIG. 2(a), a memory core 210 including a first 80-bit memory cell array 21 la and a second 80-bit memory cell array 211 b are provided for Ch-Q and Ch-P respectively. On Ch-Q, a first node 212 a of the first memory cell array 211 a is coupled to a fourth node 213 a of a first ECC control circuit 214 a for executing a SEC-DED process. A connection between the first node 212 a and the fourth node 213 a also includes 8 bits of ECC. Because the 8 bits of ECC enable a SEC-DED process for more than 72 bits, a second node 212 b of the second memory array 211 b may be coupled to a fifth node of 213 b of the first ECC control circuit 214 a to transfer extra bits. In this example, 16 data bits can be transferred between the second node 21.2 b and the fifth node 213 b. However, it will be appreciated by those of ordinary skill in the art that any number of extra bits within error correction capacity of the additional ECC 8 bits (e.g., error correction capacity of 120 bits) can be transferred between the second memory cell array 211 b and the first FCC control circuit 214 a in this manner without departing from the scope of the present disclosure. On Ch-P, a third node 212 c of the second memory cell array 211 b is coupled to a sixth node 213 c of a second FCC control circuit 214 b for executing SEC-DED process, concurrently with Ch-Q. The first ECC control circuit 214 a provides 88 bits (72 bits from memory cell array 211 a+16 bits from memory cell array 211 b) after SEC-DED process and the second ECC control circuit 214 b provides 57 bits after SEC-DED process, thus the total of 145 bits can be provided after SEC-DED process.

As illustrated by the previous example, by transferring some bits of data originally provided to the second memory cell array to Ch-P as previously described with reference to FIG. 2(b), it is possible to apply SEC-DED on more than 144 bits data of Ch-P and Ch-Q. Where bits of Ch-P are transferred to Ch-Q and both EEC channels work concurrently, a number of data bits for ECC are sufficient to support SEC-DED ECC for all of the data.

FIGS. 3(a) and 3(b) are simplified block diagrams of data bits, check bits and check matrices of a semiconductor device according to the present disclosure. FIGS. 3(a) and 3(b) illustrate matrices executed on the ECC control circuits of the error correction block 15 coupled to a memory core via multi channels as illustrated in FIG. 2(b). As shown in FIG. 3(a), 80 bits of Ch-P may be separately processed by two operational matrices. In particular, 57 bits of the 80 bits are processed by a sub-operational matrix 301 (Matrix-A ChP) and 16 bits of the 80 bits are processed by a sub-operational matrix 302. (Matrix-B). As for Ch-Q, 80 bits including 8 parity bits are processed with a third operational matrix 303 (Matrix-ChQ). Thus, the sub-operational matrix 302 becomes a part of SEC/DED ECC processing on Ch-Q as shown in FIG. 3(b). A fourth operational matrix 302′ includes an extra 1 bit “1” added on the eighth row (Row 7) of the sub-operational matrix 302 because the sub-operational matrix 302 is based on 7 bit parity and in order to be properly processed by the extended Hamming code. Thus, a first operational matrix 304 of Ch-Q includes the third operational matrix 303 (Matrix-ChQ) of Ch-Q and further includes a modified sub-operational matrix. The first operational matrix 304 is used in executing the SEC-DED process for 88 bits data including 72 bits from Ch-Q and 16 bits from Ch-P, and 8 check bits from Ch-Q. Ch-P includes a second operational matrix 301 (Matrix-A ChP) for processing 64 bits including 7 parity bits, excluding the transferred 16 bits. In the example of FIG. 3(b), operational matrices based on extended. Hamming codes for SEC-DED are illustrated. However, parity check matrices of any other ECC codes which meet a correction and detection level of SEC-DED may be used in other embodiments.

To produce syndromes based on SEC-DED on two channels it is possible to generate pre-syndrome (which may also be referred to as a “pre-parity”) 8 bits for 16 bits data on Ch-P for a SEC-DED code such as the extended Hamming code and provide the pre-parity 8 bits to Ch-Q. On Ch-Q, the 8 parity bits and syndrome for the entire 88 bits of data are generated and the syndrome provided to Ch-P. However, this pre-parity generation scheme may exceed a desired address access time (tAA) because of transmission time for sending the pre-parity 8 bits from Ch-P to Ch-Q and receiving the syndrome 8 bits from Ch-Q to Ch-P.

FIG. 4 is a schematic diagram of multi-channel error correction processes and data flows according to the present disclosure. FIG. 4 illustrates a schematic diagram of flows of data bits and parity bits among the two channels, Ch-P and Ch-Q for shortening the parity and syndrome transmission time. 64 bits including 7 parity bits in Ch-P are provided to a first parity check matrix (Hp1) 401 a to provide a first syndrome SP1 and 16 bits in Ch-P are provided to a second parity check matrix (Hp2) 401 b for generating a first pre-parity SP2Q (8 bit). 72 bits in Ch-Q (80, 72) are provided to a third parity check matrix (Hq) 401 c for generating a second pre-parity SQ2P (8 bit). The first pre-parity SP2Q and the second pre-parity SQ2P may be generated simultaneously and provided to Ch-P and Ch-Q. The first syndrome SP1 from the first parity check matrix (Hp1) is forwarded to a first corrector 403 a for detecting and correcting errors in the 57 bits using the first syndrome SP1. In Ch-P, SQ2P and SP2Q are combined at a first adder 402 a to provide a second syndrome SP2 which is forwarded to a second corrector 403 b. The second corrector 403 b executes error detection and correction of the 16 bits transferred to Ch-Q using the first syndrome SP2. In Ch-Q, SQ2P and SP2Q are combined at a second adder 402 b to provide an 8-bit syndrome SQ which is forwarded to a third corrector 403 c for error detection and correction of the 72 bits. The ECC pre-parity bits may be transmitted between the channels and the syndromes can be obtained without waiting for receiving a syndrome based on pre-parity or enhancing data widths in bits which causes area penalty. As a result, the ECC pre-parity bits may be generated in a shorter time to improve tAA.

FIG. 5 is a block diagram of multi-channel error correction processes and data flows among components according to the present disclosure. FIG. 5 illustrates a layout of ECC control circuits including components and conceptual data flows through the components. For example, first data and check bits on Ch-P are read from a first memory cell array 501 a and second data and check bits on Ch-Q are read from a second memory cell array 501 b. Typical ECC control circuits employ static exclusive-or (XOR) trees for parity computation which tend to have glitches. To reduce such glitches, signals are first provided to drivers which provide the signals' true state and complementary state. In FIG. 5, 57 data bits <D0:32> and <D40:63> of Ch-P are provided to first drivers 502 a and their corresponding seven check bits <P0:6> are provided to second drivers 502 b. Also, the 16 data bits <D64:79> on Ch-P are provided to third drivers separately from the 57 data bits because the 16 data bits are processed separately with another set of check bits stored in Ch-Q. In a meanwhile, 72 data bits <D0:31> and <D40:79> of Ch-Q are provided to fourth drivers 502 d and check bits <P0:7> are provided to fifth drivers 502 e. In this manner, each bit is provided to its corresponding driver and its true state and complementary bar state are provided as output signals from the corresponding driver to prevent effects due to glitches.

The output signals from the drivers may be transferred to ECC parity XOR blocks via data input buses. For example, the 57 data bits and the check bits of Ch-P are provided to first ECC parity blocks 504 a with 32 inputs and the first ECC parity blocks 504 a provides a first 7-bit syndrome which is used for data correction of 57 bits at first correctors 506 a. In a meanwhile, the 72 bits and the check bits of Ch-Q are provided to third ECC parity blocks 504 c with 32 inputs for generating first 8-bit pre-parity which is transferred from Ch-Q to Ch-P. The 16 data bits of Ch-P are provided to second ECC parity blocks 504 b for generating second 8-bit pre-parity which is provided from Ch-P to Ch-Q. A first XOR logic 505 a of Ch-P and a second XOR logic 505 b of Ch-Q both receive the first 8-bit pre-parity and the second 8-bit pre-parity and generate a second 8-bit syndrome. The second 8-bit syndrome generated at the first XOR logic 505 a is provided to second correctors 506 b for data correction of the 16 data bits <D64:79>. The second 8-bit syndrome generated at the second XOR logic 505 b is provided to third correctors 506 c for data correction of the 72 bits of Ch-Q. Thus, ECC memory processing of two channels with flexible code-length ECC can be achieved.

In one embodiment, as illustrated in FIG. 5, it is possible to assign storage cells of check bits in the center areas of arrays. The data input buses may have shared-bus architecture. The 57 data bits of Ch-P and their corresponding seven check bits may use a first bus 503 a, the other 16 data bits <D64:79> of Ch-P may use a second bus 503 b, and the 80 bits on Ch-Q uses a third bus 503 c. These features may contribute to high speed data transmission and layout flexibility.

In another embodiment, a plurality of independent (80, 72) channels are included, each having 8 check bits, instead of dividing a large data width into two channels. In this way, it is not possible to have a high bandwidth such as a total 145 bits including 128 data bits and 17 check bits suitable for BCH ECC; however, by having 80-bit memory cell arrays with simple SEC-DED ECC for 128 data bits, it is possible to keep same formation of both two channels.

FIG. 6 is a schematic diagram showing configurations of multi-channel error correction processes and data flows according to the present disclosure. FIG. 6 illustrates a schematic diagram of flows having 72 data bits and 8 check bits in each of the two channels, Ch-P and Ch-Q. The embodiment of FIG. 6 may be used for providing up to 144 data bits with SEC-DED ECC. 72 bits in Ch-P (80, 72) are provided to a first parity check matrix (Hp) 601 a for generating a first 8 bit syndrome SP. Similarly, 72 bits in Ch-Q (80, 72) are provided to a second parity check matrix (Hq) 601 b for generating a second 8 bit syndrome SQ. In Ch-P, the first syndrome SP is provided to a first corrector 602 a for SEC-DED process of 72 bits. In Ch-Q, the second syndrome SQ is then provided to a second corrector 602 b for SEC-DED process of 72 bits. Thus, similar channel structures may be applied across independent channels and simple designs with simple data correction may be achieved.

FIGS. 7(a) and 7(b) are block diagrams showing logic circuitry of multi-channel error correction and data flows with optional switches between two different multi-channel modes on two channels according to the present disclosure. FIGS. 7(a) and 7(b) illustrate components and data flows through the components, according to an embodiment including option switches between a 145 bit channel mode for BCH (indicated as “2Ch”) and a 72×2 bit mode (indicated as “1Ch”).

In Ch-P, as illustrated in FIG. 7(a), a first ECC Parity circuit 701 a receives data bits and parity bits of Ch-P and provides 7 check bits. At the same time, in Ch-P, a second. ECC parity circuit 701 b receives 16 bits and prepares a first pre-parity. A first option switch 702 is a multiplexer which receives a ChMode signal as a selector input indicative of either a 2Ch mode or a 1Ch mode. When the ChMode is indicative of the 2Ch mode, a second pre-parity from Ch-Q to Ch-P is provided as output signals, whereas the seven-bit check bits from the first ECC parity circuit is provided as output signals if the ChMode is indicative of the 1Ch mode. The output signals from the first option switch 702 and the output signal of the second ECC Parity circuit 701 b are used as input signals of a first XOR logic 703 and a syndrome for Ch-P is provided as a result based on the ChMode. There is a second option switch 704, which is a combination of multiplexers which receives ChMode as a selector input, and also receives the output signals of the first XOR logic and the output of the first ECC parity circuit as input signals. The second option switch 704 provides a combination of the first pre-parity and the second pre-parity as a check result in case of the 2Ch mode, whereas the second option switch 704 provides a check result of all data in Ch-P in case of the 1Ch mode.

In Ch-Q, as illustrated in FIG. 7(b), a third ECC Parity circuit 711 receives data bits and parity bits of Ch-Q and provides 8 check bits. A third option switch 712 is a multiplexer which receives a ChMode signal as a selector input indicative of either the 2Ch mode or the 1Ch mode. When the ChMode is indicative of the 2Ch mode, a first pre-parity from Ch-P to Ch-Q is provided as output signals. The output signals from the third option switch 712 and the output signal of the third ECC Parity circuit 711 are used input signals of a second XOR logic 713 and a check result for Ch-Q, either including the 16 bits from Ch-P in computation of check bits and a syndrome or excluding the 16 bits from Ch-P, is provided based on the ChMode.

In another embodiment, a faster parity/syndrome computation technique is introduced. The extended Hamming code with SEC-DED includes an extra parity bit in order to increase its minimum distance of the code which enables the code to detect two-bit errors. This extra parity bit results in a row with all “1” bit in the extended Hamming code. For example, in case of 8-bit pre-parity for 16 bits, a parity matrix as shown in FIG. 8(a). The row with all “1” bits may cause a decrease in multiple-input of XOR logic. To improve this bottleneck, it is possible to use internal nodes of other pre-parity bit generators. As shown in FIG. 8(a), by obtaining data inputs from pre-parity bits <4:6>, it is possible to cover the pre-parity information for pre-parity bit <7>.

FIG. 8(b) shows sample circuit configuration of this embodiment. ECC parity circuits 801 a, 801 b, and 801 c, the above pre-parity bit generators, receive input signals for pre-parity <4>, pre-parity <5> and pre-parity <6>, respectively. Additionally to producing pre-parity data as previously described, the ECC parity circuits 801 a, 801 b, and 801 c also provide output signals. For example, a first ECC parity circuit 801 a provides a ParX signal as a result of XOR logic from input data signals <64, 67, 68> and further provides a ParfX signal as a result of 3-input XOR logic from input data signals <57, 59, 60>. Similarly, the second ECC parity circuit 801 b provides a ParY signal as a result of XOR logic from input data signals <58, 61, 62>. The third ECC parity circuit 801 c provides a ParZ signal as a result of XOR logic from input data signals <69, 70, 72> and further provides a ParfZ signal as a result of XOR logic from input data signals <63, 65, 66>. An ECC circuit with a 6-input XOR 802 receives the signals ParX, ParfX, ParY, ParZ, ParfZ and the input data signal <71> and provides pre-parity <7> instead of taking a full weight of the code with a row with all “1”. It is also possible to include a short circuit 803 which may couple an output of its true state and an output an inverter which receives an output signal of its complementary state. This may reduce extra time of any critical node after the ECC circuit 802.

In another embodiment, as illustrated in FIG. 9, a syndrome decoder 901 in the error correction block 900 receives an 8-bit syndrome. The 8-bit syndrome is received by two NAND logics and output signals at nodes “a” and “b” of the two NAND logics are received at a NOR logic. If an output signal at a node “c” of the NOR logic which is an output stage of the syndrome decoder 901 is logic low, then data correction is not executed. If the output signal from the syndrome decoder 901 at the node “c” is logic high, error correction is executed. An error correction circuit 902 of the error correction block 900 receives four input signals: a “df” signal indicative of either read data “DR” or its complementary state “DRf”, the intermediate signals from internal nodes “a” and “b” of the syndrome decoder 901, and the output signal at the node “c” of the syndrome decoder 901.

In operation, if the output signal from the syndrome decoder 901 is logic low, the read data “DR” is provided as an output signal “Dout” of the error correction circuit 902. If the output signal from the syndrome decoder 901 is logic high, the correction is activated. The error correction circuit 902 adopts a dynamic type circuit which functions in a flip-flop manner responsive to the output signal of the syndrome decoder 901 at the node c. As described above, data corrections in the error correction circuit 902 are executed according to timings based on the output signal from the syndrome decoder 901, thus faster data error correction can be executed.

According to various aspects of the present disclosure, more information data bits for further correction with BCH code can be once checked and corrected by the extended Hamming code for SEC-DED process. By flexibly assigning error correction and detection code lengths across a plurality of channels and maximizing SEC-DED data correction to the capacity of all available check bits on a memory device, it is possible to achieve larger data parity and syndrome generation and read data correction without causing penalty of occupying a larger area on a die of the memory device while keeping shorter processing time.

Although this invention has been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the inventions extend beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the inventions and obvious modifications and equivalents thereof. In addition, other modifications which are within the scope of this invention will be readily apparent to those of skill in the art based on this disclosure. It is also contemplated that various combination or sub-combination of the specific features and aspects of the embodiments may be made and still fall within the scope of the inventions. It should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying mode of the disclosed invention. Thus, it is intended that the scope of at least some of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above. 

What is claimed is:
 1. An apparatus comprising: a first memory cell array configured to provide a plurality of first data bits, a plurality of second data bits and a plurality of first check bits corresponding to the plurality of first data bits; and a second memory cell array configured to provide a plurality of third data bits and a plurality of second check bits corresponding to the plurality of second data bits and the plurality of third data bits.
 2. The apparatus of claim 1, further comprising a first error correcting code (ECC) control circuit configured to perform a first error detection and correction operation on the plurality of second data bits and the plurality of third data bits based on the plurality of second check bits.
 3. The apparatus of claim 2, further comprising a second ECC control circuit configured to perform a second error detection and correction operation on the plurality of first data bits based on the plurality of first check bits.
 4. The apparatus of claim 1, wherein a number of the plurality of first data bits is greater than a number of the plurality of second data bits and a number of the plurality of third data bits is greater than the number of the plurality of first data bits.
 5. The apparatus of claim 1, wherein sum of a number of the plurality of first data bits, the plurality of second data bits and the plurality of first check bits is equal to sum of a number of the plurality of third data bits and the plurality of second check bits.
 6. The apparatus of claim 1, wherein a number of the plurality of second check bits is greater than a number of the plurality of first check bits.
 7. The apparatus of claim 3, wherein a maximum number of data bits that the first error detection and correction operation is configured to correct is equal to a maximum number of data bits that the second error detection and correction operation is configured to correct.
 8. The apparatus of claim 7, wherein the first error detection and correction operation is configured to correct a maximum of one data bit of the plurality of second and third data bits and the second error detection and correction operation is configured to correct a maximum of one data bit of the plurality of first data bits.
 9. The apparatus of claim 8, wherein the first error detection and correction operation is configured to detect a maximum of two data bits of the plurality of second and third data bits and the second error detection and correction operation is configured to detect a maximum of two data bits of the plurality of first data bits.
 10. An apparatus comprising: a first memory cell array configured to store a plurality of first data bits and a plurality of first check bits; a second memory cell array configured to store a plurality of second data bits and a plurality of second check bits; a first error correcting code (ECC) control circuit configured to perform a first error detection and correction operation on a portion of the plurality of first data bits and the plurality of second data bits with using the plurality of second check bits and without using the plurality of first check bits.
 11. The apparatus of claim 8, further comprising a second ECC control circuit configured to perform a second error detection and correction operation on a remaining portion of the plurality of first data bits other than the portion of the plurality of the first bit data bits with using the plurality of first check bits.
 12. The apparatus of claim 11, wherein a number of the remaining portion of the plurality of first data bits is greater than a number of the portion of the plurality of first data bits and a number of the plurality of second data bits is greater than the number of the remaining portion of the plurality of first data bits.
 13. The apparatus of claim 11, wherein sum of a number of the plurality of first data bits and the plurality of first check bits is equal to sum of a number of the plurality of second data bits and the plurality of second check bits.
 14. The apparatus of claim 11, wherein a number of the plurality of second check bits is greater than a number of the plurality of first check bits.
 15. The apparatus of claim 11, wherein a maximum number of data bits that the first error detection and correction operation is configured to correct is equal to a maximum number of data bits that the second error detection and correction operation is configured to correct.
 16. The apparatus of claim 15, wherein the first error detection and correction operation is configured to correct a maximum of one data bit of the plurality of second and third data bits and the second error detection and correction operation is configured to correct a maximum of one data bit of the plurality of first data bits.
 17. The apparatus of claim 16, wherein the first error detection and correction operation is configured to detect a maximum of two data bits of the plurality of second and third data bits and the second error detection and correction operation is configured to detect a maximum of two data bits of the plurality of first data bits.
 18. An apparatus comprising: a first memory cell array configured to provide a plurality of first data bits, a plurality of second data bits and a plurality of first check bits; a second memory cell array configured to provide a plurality of third data bits and a plurality of second check bits; a first error correcting code (ECC) control circuit configured to perform a first error detection and correction operation on the plurality of first data bits based on the plurality of first check bits; and a second ECC control circuit configured to perform a second error detection and correction operation on the plurality of second data bits and the plurality of third data bits based on the plurality of second check bits.
 19. The apparatus of claim 18, wherein a number of the plurality of first data bits is greater than a number of the plurality of second data bits and a number of the plurality of third data bits is greater than the number of the plurality of first data bits.
 20. The apparatus of claim 18, wherein a number of the plurality of second check bits is greater than a number of the plurality of first check bits. 